Smith's butterflyfish has the anterior half of the body and associated fins are dark brown while the posterior half and fins are yellow. The posterior soft rayed part of the dorsal fin and the anal finhave blue margins. It attains a maximum total length of. The separation of the two colour blocs on the body is irregular and the spines of the dorsal fin are also yellow over the brown anterior part of the body. It attains a maximum total length of.
Smith's butterflyfish occur on rocky reefs with dense growth of algae and at least a little coral. It is often encountered in large aggregations in the middle of the water column where they feed on zooplankton. This oviparous species forms pairs for breeding.